Interaction of Cm(iii) and Am(iii) with human serum transferrin studied by time-resolved laser fluorescence and EXAFS spectroscopy

The complexation of Cm(iii) with human serum transferrin was investigated in a pH range from 3.5 to 11.0 using time-resolved laser fluorescence spectroscopy (TRLFS). At pH [greater-than-or-equal] 7.4 Cm(iii) is incorporated at the Fe(iii) binding site of transferrin whereas at lower pH a partially bound Cm(iii) transferrin species is formed. At physiological temperature (310 K) at pH 7.4{,} about 70% of the partially bound and 30% of the incorporated Cm(iii) transferrin species are present in solution. The Cm(iii) results obtained by TRLFS are in very good agreement with Am(iii) EXAFS results{,} confirming the incorporation of Am(iii) at the Fe(iii) binding site at pH 8.5.